1. Field of the Invention
The present invention relates to a method and an apparatus for forming images on both surfaces of a recording medium, and more particularly to a method and an apparatus that can adjust an image forming condition when a special recording medium is used.
2. Discussion of the Background
An image forming apparatus, such as a copying machine, a printer, a facsimile, etc., can be configured such that an image is printed on both surfaces of a recording medium (hereinafter referred to as a transfer sheet). In a background image forming apparatus, a both-surfaces printing is generally performed in the following manner. Namely, an image formed on a surface of an image bearing member is transferred and fixed onto one surface of the transfer sheet. The transfer sheet having the image on one surface thereof is then reversed, for example by conveying the transfer sheet through a sheet reversing path. The reversed transfer sheet is conveyed again to an image transfer region so that another image is transferred and fixed onto the other surface of the transfer sheet.
It is a significant challenge to ensure reliability of a conveyance of the transfer sheet when the both-surfaces printing is performed in an image forming apparatus having the above-described system, because a switching of a conveying direction of the transfer sheet and a curl given to the transfer sheet while an image is fixed onto one surface of the transfer sheet are involved. Japanese Patent Laid-Open Publication Nos. 1-209470 and 10-142869 disclose a technology for performing a fixing operation of toner images, which are transferred onto both surfaces of the transfer sheet by first and second image bearing members, at one time.
According to the technology disclosed in Japanese Patent Laid-Open Publication No. 1-209470, a first image formed on a surface of a photoconductive element is transferred onto a transfer belt by a first transfer device. A second image formed on the surface of the photoconductive element is transferred onto one surface of the transfer sheet by the first transfer device. The first image transferred onto the transfer belt is then transferred onto the other surface of the transfer sheet by a second transfer device. Thus, images are transferred onto both surfaces of the transfer sheet, which are then fixed by a fixing device.
According to the technology disclosed in Japanese Patent Laid-Open Publication No. 10-142869, an image forming apparatus employs two transfer devices. The transfer sheet having color images on both surfaces thereof is conveyed to a fixing device by which the images are fixed at one time. In this apparatus, a spur having a plurality of protrusions on a circumferential surface thereof is provided as a guide member to guide the transfer sheet that has unfixed toner images on both surfaces thereof.
A side of a surface of the transfer sheet, onto which a corresponding image is transferred, is fixedly determined in the background apparatus (i.e., for example, it is determined that first page and second page images are always transferred onto the surface and underside of the transfer sheet, respectively). Therefore, an inconvenience may be caused in collating printed transfer sheets by page, depending on a manner in which the printed transfer sheet is discharged.
Japanese Patent Laid-Open Publication No. 2000-19799 discloses an image forming apparatus having a transfer sheet reverse unit to switch the manner in which the printed transfer sheet is discharged, namely, face down or up.
The switching of the transfer sheet discharging manner (i.e., face down or up) is accomplished using the transfer sheet reverse unit while the side of the surface of the transfer sheet, onto which the corresponding image is transferred, is fixedly determined.
The present inventors have recognized that when a thick and rigid transfer sheet, such as a cardboard, etc., is used, problems may arise if an image forming operation is performed in the same manner as when a normal transfer medium is used. Problems may include the transfer sheet becoming folded or jammed while being conveyed, or degradation in quality of a printed image due to an insufficient image concentration or a low level of fixing performance.
Further, the present inventors have recognized that when a long transfer sheet is used, problems may arise as to how to handle an image data that is longer than a circumferential length of an intermediate transfer belt. In addition, a fixing temperature is decreased while an image is fixed onto the long transfer sheet. A designation of a sheet feeding device and sheet discharging tray is required. An input of information that the long transfer sheet is used needs to be performed in a simple manner.
The present invention has been made in view of the above-mentioned and other problems and addresses the above-discussed and other problems.
The present invention advantageously provides a novel image forming apparatus and method wherein an appropriate image is printed even if a special transfer sheet, such as a thick and rigid transfer sheet, a long transfer sheet, etc. is used.
According to an example of the present invention, an image forming apparatus includes a first image bearing member configured to transfer a visible image onto a first surface of a recording medium, a second image bearing member configured to transfer a visible image that has been transferred from the first image bearing member onto a second surface of the recording medium such that visible images are transferred onto both surfaces of the recording medium, and a controller configured to control an image forming condition based on a property of the recording medium.